A method for contact-free and extensive layer thickness measurement, which simultaneously provides data about the morphology and the thickness of the layer, is TIC microscopy. The acronym TIC stands for “Total Interference Contrast”. This technology is a shearing polarization interferometrical process, which generally works with circular polarized or polychromatic light, and which is described in more detail in “Schey et al., Photonik 3, 42 (2004)”, for example. A TIC module such as this has been offered by Carl Zeiss for some time. In order to determine these topographies or surface roughnesses of relative flat samples, “Phase Shifting Interferometry” would be an option for the standard method, which, however, exhibits a certain sensitivity to environmental vibrations. This is a measuring method, which is used in optics (interferometry, fringe projection) and in electronics to determine the phase position of a modulated signal by way of point-wise intensity measurements.
There are similar problems with confocal measuring methods, which are based on the sequential generation of several images. These problems are generally circumvented by using methods that are based on an interferometrical one-shot measurement, digital holographic microscopy, for example. However, the equipment expenditure is very high here.
In U.S. Pat. No. 4,534,649, a polarization interferometer for profile detection is described, in which a lateral offset, that is, a “shearing” is also mentioned. No further details are provided.
Furthermore, in Jabr, Optics Letters 10, 526 (1985), a microscope is described, which is related to “TIC”, and in this context is used especially for determining surface roughnesses, wherein the roughness data are derived from intensity variations, which entails a certain susceptibility to error, with respect to detector noise, for example.